I bought a KJ last May, and did my research as well, comparing all three. I ended up with the "classic Joe" 18". From my research, it and the large BGE are pretty much equal across the board. Except price. I found that for what I can get the KJ, including the "nest" that it comes with, ash tool, and grill grabber tool (that was all standard accesories), while they also threw in a ceramic drunk chicken holder and a bag of lump charcoal. All that cost the same as just the BGE, no nest or anything else, so that's ~$100 more for the BGE with the nest. I love the KJ, and have done several different types of cooks on it, although I have failed to take pics most of the time. I liked the fact that the KJ came with a nest, since I was not ready to commit the patio space needed for a permanent table, and I can roll the grill around on the patio depending on wind and smoke direction.

I did strongly consider the Primo, as the oval shape would be great for a much larger cooking area.

As far as accessories, I haven't really bought any. I did make a heat deflector for indirect cooks by using a round cooking stone that my wife never used, 3 solid bricks, and an extra grill grate that I had. I just put the stone on the regular grilling grate, then 3 bricks on the stone, then the extra grill grate on the stones, and meat on top of extra grate. Its worked pretty well so far like that. much cheaper than buying official KJ heat deflector. 2nd picture is using my homemade heat deflector with a small wild pork shoulder.